This invention relates to manufacturing techniques used to assemble electronic components on circuit boards. In particular, this invention relates to methods of assembling electric components, especially so-called surface mount devices on circuit boards or substrates such as alumina or other types of circuit boards.
Many electrical components, such as certain power transistors, have planar connection leads which are soldered onto conductive traces on a circuit board. To conserve space on the circuit board, additional components are frequently connected directly onto these planar connection leads.
When a planar connection lead from a device such as a transistor is to be soldered onto a circuit board and another component is to be soldered onto the planar connection lead, soldering an assembly of such components becomes difficult because the solder flowing between the layered pieces is difficult to control. Prior art methods of soldering these types of connections usually required that a layer of solder be deposited onto the substrate upon which the first component is positioned. A second layer of solder or solder paste might thereafter be deposited on the first component upon which the second component was then positioned. The assembly of pieces could then be heated as a unit until the solder flowed, which upon cooling, formed an electrically bonded assembly.
A method of joining components onto planar leaded components that reduces the number of steps required to produce a solder joint would be an improvement over the prior art. Such an improvement would preferably permit more accurate control over the amount of solder between the two components being joined together as well as the solder between the substrate and the planar connector surface.